The Fastnet race was now firmly established by the 1930's after running races for several years with fluctuating numbers. The 1930 race saw six American and two French yachts competing alongside the nine British entries.

The early Fastnets saw a high proportion of yachts failing to complete the course. This was mainly due to the toughness of the course, inexperienced crews, old, slow and ill-equipped yachts and the traditional designs of the British yachts lagged behind their fellow competitors from across the pond. Bad weather was also a dominant factor and the 1931 Fastnet saw gale force conditions and many problems for participating yachts, with one person being lost overboard. The tragedy marred what otherwise would have been a classic Fastnet, as the four leading yachts raced the last miles in close company and finished within minutes of one another.

Over the next couple of decades, yacht design for ocean racers moved swiftly and the introduction of multihulled catamarans and trimarans into ocean racing was making an impact. By the 1950's synthetic fibres were introduced and more sophisticated equipment began to bring about change. By the 1960's a more ruthless attitude to racing was emerging and the competitive spirit was sharpened by the introduction of such races as the Admiral's Cup and other major events. The Fastnet of 1965 saw the design of a radical new boat - Rabbit - a 34-foot sloop, which incorporated new ideas ensuring its victory in Class III.

The 1965 Admiral's Cup had also attracted teams from Sweden, Holland, France and the US. Irish and Australian teams also took part as relative newcomers. In 1967 the Australians took the Admiral's Cup trophy back to Sydney showing they were now in the same league as the Americans and Europeans.